The existing electronic systems employ multiple DC-to-DC converters to convert a main bus voltage from a power source supplying the system to one or more voltages required for driving integrated circuits in the electronic systems. Switching regulators, also referred to as DC to DC converters, are used to convert an input supply voltage to a desired output voltage at a voltage level appropriate for integrated circuits in an electronic system.
In most cases, a pulse width modulation (PWM) switching regulator is used to supply digital core circuitry. On the other hand, an I/O interface circuit remains turned on during a standby mode of operation. Thus, the I/O interface circuit requires a power supply capable of delivering high efficiency to a normal load as well as to a light load. In order to meet the requirements of the “green” regulations, a power supply for the I/O interface circuit needs to have high efficiency at the light load condition when the system is in the standby mode. In most cases, a pulse frequency modulation (PFM) switch regulator is desired for high efficiency light load operation.
Here, in a light load condition, when a circuit enters a PWM mode from a PFM mode, a zero-crossing detection circuit is generally turned off, and a lower-bridge circuit is turned on to enter the PWM mode. However, a voltage drop in the output voltage may occur, and a level of the voltage drop would be determined based on a loop response speed.
Therefore, in order to overcome the above-mentioned issues, improving the circuit design has become one of the important issues to be solved in this field so as to reduce the voltage drop generated under light load or no load conditions.